1. Field of the Invention
The present invention relates to an interface module for use in LSI packages, for connecting a plurality of high-speed signal-processing LSIs, and to an LSI-incorporating apparatus that has the interface module.
2. Description of the Related Art
In recent years, LSI packages have been proposed, in which a module of optical-connector type connects the LSIs and the optical waveguides can therefore be disconnected from the LSIs (see Nikkei Electronics No. 810, p. 122, FIG. 4, Dec. 3, 2001). Apparatuses have been proposed, in which an LSI package and an interface module can be electrically connected and disconnected and optical waveguides (e.g., optical fibers) are directly connected to the interface module (see Jpn. Pat. Appln. KOKAI Publication 2004-253456).
The LSI package disclosed in Nikkei Electronics No. 810 can hardly be mounted on a printed circuit board in the same way as ordinary LIS packages. To mount the package incorporating an optical module of connector type on the board, special steps must be performed in view of the optical axis displacement due to the heat resistance and heat hysteresis of the optical module and the difference in thermal expansion between the LSI package substrate and the optical module. Further, special solder must be used at specific temperatures in order to mount the package on the board. It is therefore difficult to amount the optical module on the printed circuit board in the mass-production line. Moreover, an optical connector must be used to connect the LSI package to the printed circuit board permanently, so that the optical waveguides may be disconnected when necessary. The use of the optical connector inevitably increases the material cost and process cost very much.
Neither material cost nor process cost would not increase so much in the manufacture of the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication 2004-253456 as in the manufacture of an LSI package mounted on a printed circuit board. However, the optical waveguides may fail to support the interface module, which is relatively heavy. The optical waveguides will be broken if the interface module is handled in an inappropriate manner. Other lines that need not be optically connected by all means, such as lines for supplying low-speed signals, e.g., control signals, are provided on a printed circuit board and electrically connected to the LSI package. Since these lines have different lengths on the printed circuit board, the control timing may shift. Further, these lines may pick up noise (power-supply noise, switching noise and the like), possibly causing the LSI package to malfunction.